Recently, the electronic products grow up rapidly, for the higher requirements of a flat-panel display the conventional cathode ray tube (CRT) display can not meet the market demands. A light, thin, saved electricity, and high pixel flat-panel display will become a main stream in the future display. A thin film transistor liquid crystal display (TFT-LCD) industry is developing vigorously, since the production cost is still very high, and the pixel quality and reaction rate functions still need to be promoted, many research institutes devote to developing a new generation flat-panel display, and an OLED possesses advantages such as self-emitting light, speed reaction, wide view-angle, high resolution, high brightness, etc. be viewed as a brand-new applied technique for display. Advantages of OLED are without a back light source, a self-emitting light, a simple structure, and no view-angle limit. The principle of organic electroluminescent display is to employ an electroluminescent device, when a potential is applied in the presence of an electrical field, an electron and a hole moves from anode and cathode, respectively, then recombine together in an emitting-light layer to form an excition, afterwards, the energy releases in terms of irradiation. In general, an OLED structure is shown as in FIG. 1, wherein on a glass substrate it sequentially forms an ITO transparent electrode, an organic light-emitting layer (usually the combination of a hole-transport layer and a light-emitting layer), and a conductive layer.
FIG. 2 illustrates when an organic light-emitting layer forms in a convex ITO transparent electrode area, its thickness is much thinner than that of a transparent electrode, hence it breaks down very easily to cause a signal lost or weaken; especially when the convex edge of a convex ITO transparent electrode is a sharp shape, it easily results from a signal lost or weaken.
In order to avoid causing the said of situation hence an idea to employ an insulating film between two electrodes was demonstrated in some references. U.S. Pat. No. 5,994,836 employs a negative photoresist to be as an insulating film, wherein the smoothness and an inclining angle of transparent electrode will be an important effect to influence the yields. Formation of an inclining angle for a negative photoresist is controlled by the fabrication conditions such as an exposing energy, a developing time, and a concentration of developing solution, the fabrication controlled conditions and the control of the film thickness must be very careful, otherwise it easily causes an excessive exposure to result from a larger inclining angle or a photoresist residual. U.S. Pat. No. 6,222,315 employs a polyimide (PI) resin to be as an insulating film, wherein it employs a photoresist coated on a PI film and utilizes a photolithography technique to obtain a photoresist be formed a mask, then etches PI film by way of controlling etching time and the concentration of an etching solution to control an inclining angle. The inclining angle is easily controlled, but it needs somemore annoying steps in the fabrication.